Breast pumps are well known devices for extracting milk from the breast of a user. A breast pump may be used if the baby is not itself able to extract the milk, or if the mother is separated from the baby, for example if away from the baby at work. The use of a breast pump to extract milk may also be used to stimulate and increase milk production in women with a low milk supply.
Conventional breast pumps make use of a vacuum to induce milk extraction from a nursing mother's breast. The pumping action of the device draws the milk from the nipple to a collection vessel, and the pressure and/or frequency may be adjusted to the preferences of the mother. Therefore, the adjustability of the breast pump to the preference of the mother is limited.
A conventional breast pump for extracting milk from a user's breast is shown in FIG. 1. Such a conventional breast pump unit 1 comprises a main body 2 and a feeding bottle 3. The feeding bottle 3 is attached to the main body 2 by a screw fitting.
A vacuum pump unit (not shown) is formed in the main body 2 to create a vacuum, as will be described hereinafter and a handle 4 extends from the main body 2. Breast pumps may be manually operated, for example by squeezing the handle or by operation of a foot pedal. Breast pumps may also be electrically driven by a small electric motor.
A breast-receiving funnel 5 is fixedly attached to the main body 2 for receiving the breast of a user. The funnel 5 comprises a mouth 6 and a throat 7. The mouth 6 is open at an outer end and an inner surface of the mouth 6 converges from the outer end towards the throat 7 to form a hollow recess. An insert 8 is insertable in the mouth 6 of the funnel 5 in an attempt to improve a user's comfort and aid the expression of milk. Such an insert is known from EP 1 593 402, in which an insert has a circle symmetric flexible membrane extending around an inner portion of a mouth of a funnel of a breast pump from the outer end to the throat of the funnel. The membrane is deformable into the hollow recess during use to apply a compressive force to the nipple and/or areola in an attempt to aid the expression of milk from the breast.
However, a problem with the breast pump described above is that users are known to suffer from discomfort or difficulty when using such a breast pump. When an infant feeds from its mother's breast, the baby applies two actions to obtain milk, a sucking action and a peristaltic movement created by the action of the infant's tongue on the nipple and areola of the mother's breast. The sucking action applies a negative pressure to latch onto the breast and induce milk flow. The infant can also perform a peristaltic tongue motion over the areola and nipple to induce milk flow from the breast. In this motion a rhythmic contraction and expansion motion is performed to induce the milk flow.
The peristaltic tongue motion stimulates the hormone-production responsible for the ‘let-down’ reflex which allows milk produced in the milk glands to be released into the milk ducts. Conventional breast pumps do not produce this peristaltic motion, and so the absence of such an action means that extracting milk can be uncomfortable and inefficient.
In an attempt to deal with these problems, a breast pump is disclosed in U.S. Pat. No. 4,263,912 which attempts to apply a peristaltic motion to a breast. The breast pump disclosed in this document has a circle symmetric flexible membrane with a varying thickness of membrane which increases from an outer end to an inner end of the mouth of the funnel so that the membrane is urged to deform into a nipple receiving space during use in a predetermined peristaltic manner, starting at the outer end of the funnel and deforming towards the inner end, proximate to a nipple end of the breast received in the funnel.
However, disadvantages of the above breast pump arrangement include the breast pump having a complicated construction and it is difficult to achieve a satisfactory peristaltic motion which is analogous to the action of a suckling infant.